Use of Open Surface Plasmon Resonance (OpenSPR) to Characterize the Binding Affinity of Protein–Protein Interactions

Surface Plasmon Resonance(SPR) is a label-free optical technique to assess protein–protein interaction kinetics and affinities in a real-time setting. Traditionally, Biacore SPR employs a continuous film of gold to detect any change in the angle of re-emitted light when the refractive index of a ligand conjugated to the flat gold surface is altered by its interaction with a local analyte. In contrast, the Nicoya Lifesciences’ OpenSPR technology uses gold nanoparticles to detect small changes in the absorbance peak wavelength of a conjugated ligand after its engagement by an analyte. Specifically, when broadband white light is shone onto the gold nanoparticles, it produces a strong resonance absorbance peak corresponding to the refractive index of a ligand conjugated to the surface of gold nanoparticles. Upon its interaction with an analyte, however, the absorbance wavelength peak of the conjugated ligand will be changed and timely recorded as sensorgrams of dynamic ligand–analyte interactions. Thus, the improvement in the detection method (from traditional detection of changes in the angle of re-emitted light to the contemporary detection of changes in the wavelength of the absorbance peak) features OpenSPR as a cost-effective and user-friendly technique for in-depth characterization of protein–protein interactions. Here, we describe the detailed method that we used to characterize procathepsin L (pCTS-L) interactions with two putative pattern recognition receptors (TLR4 and RAGE) using the 1st generation of Nicoya Lifesciences’ OpenSPR instrument with a 1-channel detection. Key features • Nicoya OpenSPR is a benchtop small-size equipment that provides in-depth label-free binding kinetics and affinity measurement for protein–protein interactions in real-time fashion. • This technology is relatively intuitive and user-friendly for scientists at any skill level. • OpenSPR sensors employ nanotechnology to reduce the cost of manufacturing complex optical hardware and Sensor Chips, and similarly reduce the consumption of precious analyte samples. • The manufacturer provides online training for OpenSPR (Catalog: TRAIN-REMOTE) and TraceDrawer (Catalog: TRAIN-TD) to customer scientists.